Overview
Introduction
IoTDA uses topics to communicate with devices connected using MQTT. There are custom topics and system topics. System topics are basic communications topics preconfigured on the platform. You can also customize topics on the platform based on service requirements. Note that messages through both custom topics and system topics are transparently transmitted on the platform, which means that the platform does not proactively parse data content.
After August 31, 2025, topic verification for custom topics will no longer be available to new users. It is recommended that you use device topic policies instead. For details, see Overview.
| Category | Description | Scenario |
|---|---|---|
| System topic | The platform predefines topics for communications with devices. For details of the topic list and functions, see Topics. | Message reporting, property reporting, command delivery, and events |
| Custom topic | You can customize topics for device-platform communications. Types of custom topics:
| Scenarios where services require specific topics, such as M2M communications, broadcast communications, and device migration. |
Scenarios
- Devices publish messages to custom topics. Applications smoothly forward data to message middleware, storage, data analysis, and service applications.
- Applications publish messages to a custom topic by calling APIs (see Delivering a Message to a Device). Devices subscribe to this topic to receive messages from the server.
- M2M communications, broadcast communications, and device migration.
Constraints
- You can define a maximum of 50 custom topics for a product model.
- Custom topics are only available for message communications.
- Maximum length of a custom MQTT topic: 128 bytes.
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